The information "77% of 433,000" contains the sample size number (433k). "100% of 333,410" does not contain a sample size number. The lack of the sample size number makes the data (and title) less meaningful. I'd go as far saying it makes the data (and title) meaningless.

Those means different things.

Their wording means "we checked X sites and 77% of them met some criteria", which can be extrapolated to higher values of X (assuming the proper statistical care is taken, etc).

Your wording implies the same, but that's not good because you can't extrapolate to a larger X. You chose the sites after knowing they already met the criteria, and that changes the meaning.

I get the sense OP was being a bit snide

The snide version would be "100% of 433,000". (Which is what I initially parsed it as, and nodded in agreement...)

I thought exactly the same thing but wasn't dedicated enough to do the calculation.